Trident Fleximix Power Mod

[CiaoPatsy]

Hey guys, I have a Trident Fleximix I'm in the process of bringing back to life and I would really like to get this desk running off of +16/-16v straight in rather than the 40v in thats then converted to +16/-16v  on each of the channels. It's hard to find a power supply with that voltage and also a lot more expensive than just finding an Acopian that can do 16v.

I've heard of people doing this but I'm not really sure how. I've included the schematics for a normal mic/line input channel. Let me know any ideas!

 

[joaquins]

Inverting input stage with 12k resistor in series with the mic transformer, plus one side of the transformer unconnected, it goes to ground but still. 10V phantom. There's something wrong with that input stage... I would have second thoughts about it.

About the PS, you could have anything supplying the correct voltages I guess.

JS

 

[mjrippe]

The input stage issues are well documented elsewhere.  As for the PSU, I have used a Power One +48v open frame supply trimmed down to +45v and bypassed the crowbar circuit in the chassis of the console. You can do +/-15 or 16v but it involves a bit of rewiring and modding the PCBs of each channel.  Then if anyone plugs in a non-modded channnel there will be smoke.

 

[CiaoPatsy]

Thanks for the replies.  I was messing with a stock input channel yesterday  and put +/- 15v through it.  After the voltage reduction section I was getting +/- 12v and the channel was working fine.  I'm wondering if all it will take is to use lower value power input resistors for R19 and R20 (Jim Williams suggests 10 ohms - not sure if this is with the normal supply 45v or not) to run off of +/- 15v? Gotta mess with it unless you can describe the specific mods to do  each channel